Yes — hair can both accumulate mercury and be affected by high exposures. Mercury (especially methylmercury) deposits in hair and is used as a biomarker; significant or chronic exposure may contribute to hair thinning or loss alongside systemic symptoms. Typical low-level environmental or dietary exposures usually do not cause noticeable hair changes.

Hair mercury is measured in micrograms per gram (µg/g or ppm). Levels below about 1 µg/g are generally considered low. Concentrations around 1–2.5 µg/g indicate moderate exposure; levels above roughly 2.5–3 µg/g are concerning—especially in pregnant women and children. Values over 10 µg/g are widely viewed as high and associated with increased risk of mercury toxicity.

To test hair for mercury, consult your clinician to choose an accredited lab and appropriate test (hair reflects longer-term exposure, especially methylmercury). A technician cuts 1–3 cm of hair from the occipital scalp as close to the root as possible, about 50–100 strands (~100 mg). Avoid recent chemical treatments and document product use. Labs report levels and clinicians interpret clinical significance.

Mercury most severely damages the nervous system, particularly the brain and developing fetal/child nervous systems. Inhaled elemental mercury vapor crosses the blood–brain barrier and concentrates in the brain; organic forms (methylmercury) also target the central nervous system, impairing cognition and motor function. Kidneys are another major target, and acute inhalation can severely affect the lungs and respiratory tract.

How long will mercury stay in your body? It depends on the form: methylmercury (from fish) has a blood half‑life of about 40–70 days, so it can take several months to largely clear. Elemental and inorganic mercury can accumulate in kidneys and brain and may persist for months to years. Clearance varies with dose, exposure route, individual factors, and if chelation is used.

Modern commercial hair dyes do not contain mercury. Historically some cosmetic products used mercury compounds, but these are banned in many countries. Hair itself can accumulate mercury from environmental or dietary exposure, so hair tests can detect mercury levels. Rare illicit or unlabeled products might contain prohibited mercury compounds—avoid unknown sources and check ingredient lists or consult a dermatologist if worried.